Telephone system



Dec. 29, 1925- 1,567,282 H. W. M DOUGALL TELEPHONE SYSTEM Filed Dec. 19 I 1921 3 Sheets-Sheet l y Affjr.

'Dec. 29,1925- 1,567,282

r H. w. M DOUGALL TELEPHONE SYSTEM Filed Dec. 19 1921 3 Sheets-Sheet 2 Vania/1' &

' Dec. 29,1925- 1,567,282 I H. W. Ma DQUGALL TELEPHONE SYSTEM Filed Dec. 19, 1921 3 Shets-Sheet 5 70 0 Erie ri //7 en/an fiarry 14 Maria/y? y Wm/y' HARRY W. MAQDOUGALL, OF,EA$5T GRANGE. NEW] JERSEY, ASSI J-HOR TO WESTERSE ELECTRIC COMPANY, INCQRJPOEATED, 61* NEW' YDRK, N. T71, A. CORPORATIGN OF NEW YORK.

TELEPIE-IDN E SYSTEM.

Application filed ficccinber 13, 1.92

'Fetate ot New Jersey, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

T his invention relates to telephone systems and more particularly to such systems in which the signals for a plurality of trunk lines extending between widely separated stations are controlled over a single signaling path common to such trunk lines.

In systems of this character repeater equipments may be included in the trunk line at intermediate stations, and in order to economize on these equipments it is desiraole that the filament circuits of the vacuum tubes employedtherein shall be completed only when the trunk line, of which they are a part, is in use.

The present invention is a continuation in part of my application filed December 23, 1919, and bearing Serial No. 34%,900.

it is the object of this invention to prov e improved means for and methods of associating the common signaling path with the particular trunk line taken for use, for controlling the filament circuits of the repeater equipments in this trunk line and for operating signals associated with the selected trunk line over the common signaling path.

The means provided by the present invention for attaining this object will be more read-"1y understood by reference to the accon'ipanying drawings in which Figs. 1 to i when arranged with Fig. 2 to the right of Fig. 1 and Fig. 3 to the right of Fig. 2, are a diagrammatic representation of a telephone system en'ibodying the present invention. F 1 shows the equipment located at an otiice X. Fig. 2 shows that at an intermediate repeater station Y and Fig. 3 shows that at an otlice Z. Although but one iepeater station Y is shown, it will be apparent from the subsequent description that number of such stations might be employed. A single trunk line L terminating in jacks and 110 at otlices X and Z respectively and in multiple jacks is shown, but in practice many such lines would be assoc'i ted with a single signaling path com- Serial No. 523,264.

men to a group of lines. Only the ends oi cord circuits A and B which cooperate with the trunk lines L are shown, as their other ends may be of any design suitable for cooperating with subscribers or local trunk lines terminating in the offices X and Z.

In order that signals may be sent in either direction, duplicate apparatus is provided, that located at ot'fice X and employed in establishing connections from oitice X to ofiice Z hein designated by numerals under 100, each corresponding piece of apparatus at oitice Z or employed in signaling therefrom to oliice X being numbered one hundred more than the piece to which it corresponds, for example, jack 110 at ofiice Z corresponds to jack 10 at ottice X. As these corresponding parts are identical in structure and function, but one set will be described.

in the lower left hand dotted rectangle in Fig. l is shown a selector switch 30, having an arm driven by a self-interrupting magnet 34 over contacts individual to the various trunk lines of the group. In the right hand dotted rectangle is shown a se lector switch 40 having arms 4.2 and 43 which are moved sin'iultaneously by motor magnet 47 over their associated contacts also equal in number to the lines in a group. A selector switch 50 having an arm 5 1irotated over its contacts by motor magnet 53 is shown below the dotted rectangles. To allow simultaneous signaling in both directions there is provided the usual duplex equipment comprising ditlerentially wound polarized relays 28 and 29, metallic conductor 80, and balanced artificial line AL. As the specific telephone repeater circuits form no part of the present invention they have been indicated by the dotted rectangle RI, only the ends of the filament circuits. terminating in contacts of relays and 170, being shown.

It is believed that the invention will be readily understood from a consideration of the description of: the operation of the system which is as follows:

Operator (at 077606 X initiates a call.

'lf he operator at ollice X, desiring to communicate with the operator at ofiice Z, inserts'plug 1 oi a link circuit A at ofiice X into jack 10 of line L Relays 2 and 11 tl'iereupon operate over a circuit extending i'rom battery through the winding of relay 5-), the sleeve contacts of plug 1 and jack 10, and the winding of relay 11 to ground. In closing its right-hand alternate contact, relay 11 operates busy signals 72 associated with the mutiples of jack of which one is shown, over a circuit extending from ground, the right-hand alternate contact of relay 11, the normal contacts of relays 13 and 14; to battery through the windings of the various signals 72. Relay 12 also operates over an obvious circuit closing the circuit for and starting the operation of motor magnet 53%, such circuit extending from battery through the winding and contact of motor magnet 34-, the normal contact of relay 31, and the right-hand alternate contact of relay 12 to ground. The operation of relay 12 also energizes relay 13, whereupon the ground for maintaining the signals 72 operated is transferred to the continuity contact of relay 13. Immediately upon inserting the plug 1 into the ack 10, the operator aetnates ringing key 3, causing the operation 01 relay 23 over a circuit extending from the source of alternating current through the loweralternate contact of key 3, the ring contactsof plug 1 and jack 10, lower normal contact of relay 18, the condenser 24, the winding of relay 23, the upper normal contact ot'relay 18, the tip contacts of jack 10 and plug 1, and the upper alternate contact of key 3 to ground. Relay 22 thereupon op crates over an obvious circuit and locks in an operated condition over a circuit extending ttrom'battery through the winding and upper alternate contact of relay 22 and the right-hand normal contact of relay to ground. The closure of the inner alternate contacts of relay 22 short circuits the windings of the repeating coil to prevent the trzmsmission of the ringing current therethrough while the closure of the lower alternate contact of relay 22 connects ground through the winding of relay 20 to the terminal individual to line L of selector switch 30.

In response to the operation of the motor magnet 3 the arm 33 travels over the bank 01 contacts of the selector switch 30, and when itengages the contact individual to the line L relays 31 and 20 operate over a circuit established from battery through the winding of relay 3]., the arm 83 of the selector switch and the contact engaged thereby, the winding of relay 20 and the lower alternate contact of relay 22 to round. The opening of the normaloontact of relay 31 disables the motor magnet 34 and permits the arm 38 to remain in engagement with the contact indi vidnal'tothe line L Relay 31 locks-over a vcircuitextending from battery. through the winding .andthe left-hand alternate contact of'relay 31 and the contact c1" relay to ground. The closure of the right-halal alternate contact oi relay 3i closes a circuit or the motor magnet -1 oi the selector switch 4.0 which extends from battery through the winding and contact of motor magnet 47, the letthand normal contact of relay 41, and the righthand alternate contact 011 relay 31. The motor magnet all thereupon causes the synchronous rotation of arms 42 and 4-3 which are mounted upon the same shaft of the selector switch.

In operating, relay 2O closes its alternate contacts and opens its normal contacts, the closure of the left-hand alternate contact thereof connecting the positive terminal of battery to the interconnected terminals of the terminal bunk associated with the arm 4-3. The closure of the middle alternate contact of relay 20 connects ground to the terminal individual to the line L of the terminal bank associated with the arm 1-2. The opening oi the right-hand normal contact and the closure of the right-hand alternate contact of relay 20 provide a substitute loci:- ing cir uit for relay 22 which extends from battery through the winding and upper alter nate contact of relay 22, the right hand alterrate contact of relay 20, the right-hand normal contact oi relay 41, and the contact ot relay 15 to round. The arm 2L2 rotates until it engages the terminal individual to the line L whereupon relay 41 operates over :1 circuit extending from battery through the winding 01 relay &1, the arm 42 and the contact engaged thereby, and the middle alter rate contact of relay 20 to ground. The opening of the left hand normal contact: of relay 41 disables the motor magnet 47 so that arm remains in engagement with the terminal individual to the line L The opening oi the right-hand normal contact ot relay 4i]. releases relay 22, and the closure oi the right-hand alternate contact of relay ll operates relay 44 over a circuit extending from battery through the winding oi relay 44;, the right-hand alternate contact of relay 41, and the contact of relay 45 to ground. lelay at thereupon looks over a circuit extending from battery through the winding and left-hand contact of relay 14. and the contact oil relay -15 to ground. The release oi relay role 5 relay 20. The release o'i ielay 2O removes the ground from the terminal individual to the line L oi selector switch 40, so that relay ll releases, tlmrelrr ccm 'ilet-ing the operating circuit oi motor magnet 47, so that arms 12 and 1-3 of the selector switch continue in their rotation. Upon arm d2 engaging the last terminal oi the bank, relays 4-5 and ll operate over a circuit extending from battery through the winding oi relay l1. the contact arm 42 and the terminal engaged thereby, the right-hand contact oi relay :1, and the winding of relay to ground. The operation oi relay releases relays 4:46 and 31 and the release of the (ill relay er in turn releases relays l1 and 15. The release of relay 31 againestablishes the circuit for magnet 3% so that the selector switch will continue to operate as long as plug 1 remains in incl: 10, but will perform no function until one of its contacts is grounded either by the seizure of another line or by the transmission of other l by the operator at A. Each time that the arm 43 engages a terminal of the associated bank prior to its engagement with the terminal corresponding to the line 1L an impulse o'lf current of positive polarity is transmitted over the duplex equipment comprising relays and 29, common signaling conductor 80 and the artificial lines indicated at All. lhese impulses pass over a circuit extending from positive terminal of battery through the left hand alternate contact of relay 20 the terminal engaging contact arm d3 of the selector 40, from thence over one path through the lower winding of relay 28 and the artificial line to gr und and over another path tl'irough the upper winding oi? relay 28 the common signaling conductor 80, the upper winding of relay 29, the lower winding of said relay, and through the artificial line AL to ground. The direction of the current flowing through this circuit causes the relay 29 to close its lower contact but leaves relay 28 inert. In response to the first of such impulses relay 67 is operated over a circuit extending from beta through the contact and winding of motor magnet 68 associated with the selector switch 60, the right-hai'ld winding of relay 67 and the lower contact of relay 29 to ground. Relay 67 thereupon locks over a circuit established from battery through the left-hand winding and lettdland contact oi relay 6'? and the contact of relay 6% to ground. Motor magnet 68 responding to each closure of the lower contact of relay 29 causes the synchronous rotation of arms 61 and 62 of the selector switch 60. Therefore, the arms 61 and 62 will be advanced corresponding to the number of impulses transmitted by the arm d3 of the selector switch 10, and upon the completion of the series they will rest upon terminals corresponding to the line ll 'llhereupon slow relay 71 operates over a circuit extending from battery through the winding ol relay 71, the terminal individual to the line L otthe bank associated with the arm 61., and the arm 61 to ground. Relay 7O thereupon operates over a circuit extending from battery through the winding of relay '70, the right-hand alternate contact of relay 71. and the left-hand normal contact of relay 66 to ground. Relay 70 in operating looks over a circuit extending from battery through the winding and uric dle contact ct relay 70 and the leftrhand normal contact of relay 66 to ground. The closure of the left-hand alternate contact of relay 70 complates the filament current supply circuit of the repeater B which is associated with the line L so that such repeater is adapted for operation in connection with conversations over the line. The repeater B may be similar in all respects to the repeater shown in Fig. 3 of United States Patent No. 1,413J08, granted to John Davidson, Jn, April 25, 1922. The closure of the left-hand alternate contact of relay 71 causes the operation of relays and 63 over a circuit extending from battery through the winding oi? relays 65 and 63 in series, the left-hand alternate contact of relay 71 and the contact of relay 64 to ground. Relays 65 and 63 are loch-ed in a circuit from grounded battery through the winding oil relay 65, the winding and right-hand alternate contact of relay 63 to ground at the contact of relay 6 1-. The opening of the right-hand normal contact of relay (5 disconnects positive battery from the interconnected terminals of the bank associated with. the arm 62 over a circuit extending from the positive terminal of the battery through the right-hand contact of relay 67 and the right-hand contact of relay 65. The closure of the right-hand alternate contact of relay 65 connects ground to the interconnected terminals associated with the arm The closure of the left-hand alternate contact of relay 65 completes a circuit for motor mech anism 68 extending from battery through the contact and winding of motor mechanism 68, the left-hand alternate contact ot relay 65, and the normal contact of relay 64c to ground. Thereupon the arms 61 and 62 continue in their rotation until they on gage the last terminal of the associated banks. In passing from the contact associated with the line L arm 61 interrupts the circuit of relay 71, which opens its righthand alternate contact to break the original energizing circuit for relay 70 which, however remains loclred up to ground on the outer left hand armature and normal contact 0t relay 66. Relay 71 in closing its normal contact also completes a circuit from battery through the winding of relay 70, the normal contact of: relay 71, and the righthand alternate contact of relay 70 to ground. In engaging the last tern'iinal oi. its associated bank arm 61 completes an operating circuit for relay 6+1, which may be traced trom battery through the let'tlrand alternate contact of relay 62:3. the winding of relay 6 1 the last terminal oi? the bani: associated with the arm 61, and the arm 61 to ground. The motor mechanism 68 is thereupon disabled and relays 68 65 and 6? are released, the release. of relay 63 causing the release of relay 64.

Upon each engagement of the arm fwith a terminal ott-he associated bank prior to its engagement with the contact corresponding to the line L an impulse of current of positive polarity is transmitted over the circuit extending'from the positive terminal of the battery through the right-hand contact of relay 3?, the right-hand normal contact of relay o5, the engaged terminal of the bank, the contact arm 62, the upper wine g of relay 128, the common signaling conductor 180, the upper winding of relay 19), the lower winding of said relay, through the artificial line AL to ground. Each such impulse of current causes the relay 129 to close its contact completing a circuit for motor magnet 153 extending from battery through the contact and winding of motor magnet 153 and the contact of relay 129 to ground. In response to the operation of the motor magnet 153, the arm 15 1 advances. Upon the completion of the series being transmitted, the arm rests upon the terminal which is individual to the line L whereupon relay 119 operates over a circuit extending from battery through the winding of relay 119, the terminal individual to the line L and the arm 154 to ground. In operating, relay 119 causes the operation or" relay 118 over an obvious circuit which causes the operation of relay 117 over a circuit extending from the source of alternating current through the lower alter nate contactof relay 118, the right-hand normal contact of relay 111, the right-hand winding of relay 117, and the upper alternate contact of relay 118 to ground. Lamp 116 is thereupon lighted over a circuit extending from battery through the contact of relay 117 to ground, and busy signals individual to each multiple of jack 110 are operated over a circuit from battery through the windings of magnets 172, the normal contacts of relays 114 and 113, the left-hand normal contact of relay 111 and the contact of relay 117- to ground. Relay 17 is looked over a circuit extending from battery, through the middle normal contact of relay 111, the left-hand winding and contact of relay 117, to ground. Relay 151 operates over a circuit extending from battery, through the winding of relay 151, the middle alternate contact of relay 118, and the normal contact of relay 152 to ground and locks through its middle alternate contact. Motor magnet 153 thereupon begins operating over a circuit extending from l .ery, through the contact and winding or motor magnet 153, the left-hand alternaie contact of relay 151 and the normal contact oi relay 152 to ground. Arm 154 is thereby caused to continue in its rotation until. it engages the last terminal of the associated bank, whereupon relay 1.52 operates over a circuit extending from battery, through the right-hand alternate contact of menace relay 151, the winding of relay 152, the lcrininal ot' the bank engaged by arm 15-1, and the arm 154; to ground. Relay 151 thereupon releases, and in releasing causes the release of relay 152 and stops the operation of motor magnet- 153.

Operator at ofiice Z answers the ca.

Observing the lighted condition of lamp 110, the operator at ofiice Z inserts plug 101 of link circuit B thereat into the jack 1.10 of line circuit 1). Relays 102 and 111 operate over a circuit extending from battery, through the winding of relay 102, the sleeve contacts of plug 101 and jack 110, and the winding o't relay 111 to ground. The closure of the right-hand alternate contact of relay 111 causes the operation of relay 112 which in closing its right-hand alternate contact causes the operation of relay 11? and at its left-hand alternate contact completes a circuit for the motor magnet 131 of the selector switch 130. In response to the operation of magnet 13 1 the arm 133 is rotated over its contacts, but as relay 122 inert, no circuit will be completed for relay 131 and no signal will be sent out at this time. The opening of the middle normal contact of relay 111 releases relay 117, thereby extinguishing lamp 116. However, the busy signals 172 are maintained in an operated condition over a circuit traceable from battery through the windings of magnets 172, the normal contacts of relay 114. and the continuity contacts of relay 113 to ground. The opening of the right-hand normal contact of relay 111 removes the right-hand operating winding of relay 117 from its bridged relation across the conductors of line circuit D. By the actuation of the listening key 104 of the link circuit B, the operator at oflice Z thereupon enabled to communicate with the op erator at oliice X.

Operator at oflicc X 'rcrz'ng's for lighting the superm'sorg signal at office Z.

In case the operator at oliice X desires to signal the operator at ollicc Z attcr connection has been made with the line circuit L atboth otlices, the operator at oliicc X aclu ates the ringing key 3 oi the line circuit A, thereby causing the operation oi ringing response relay 23 as previously described to transmit a series of impulses through the selecting apparatus to the otlice Z in a manner similar to that described in connection with the initiation of the all. However, since the relay 117 is no longer operatively associated with the line circuit L it does not operate, but the supervisory relay 100 in the linl: circuit B is operated over a circuit extending from the source of alternating current through the lower alternate con tact of relay 118, ring contacts of jack 110 and plug 101, the lower normal contact of ringing key 103, the right-hand winding of relay 106, the condenser 107, the upper normal contact of key 103, the tip contacts of plug 101 and ack 110, and the upper alternate contact of relay 118 to ground. Lamp 105 is thereupon lighted over a circuit extending from battery, through the alternate contact 0: relay 102, the normal contact of listening key 104, the lower contact of relay 106, and the lamp 105 to ground. The operator at ofiice Z, observing the lighted condition of the lamp 1.05, act-uates listening key 104 so that she may communicate with the operator at oliice X. The actuation of the listening key 104 in addition to connecting the usual operators telephone set (not shown) with the talking conductors of the line circuit also extinguishes lamp 105 and releases relay 106.

Operator at ofiicc If disconnects.

Upon the completion of the conversation, the operator at oilice X actuates ringing key 3 to transmit a disconnect signal to the op eratorat oiiice Z in exactly the same manner as that described in connection with the reringing of the operator at oilice Z. The plug 1 may be removed from jack 10 as soon as'key 3 has been actuated, whereupon relays 2, 11 and 12 release. Relay 13 also releases due to the release of relay 12 and as such relay is slow in releasing, relay 14 operates over a circuit extending from bat tery, through the winding of relay 14, the left-hand contact of relay 13, and the normal contact of relay 12 to ground. Relay 14., thereupon locks in an operated condition over the circuit extending from battery, through the winding and an alternate con-- tact of relay 14, and the right-hand normal contact of relay 21 to ground. The closure of contact 73 of relay 14 provides a substitutc c'rcuit to maintain the busy signals 72 operated until the apparatus is completely restored, after the release of relay 11 opens their original circuit. The closure of the outer right-hand alternate contact of relay 14 connects ground from the normal contact of relay 22., through the right-hand alternate contact of relay 14 and the winding of relay 21 to a terminal of the selector switch 30 individual. to the line L The closure of the left-hand alternate contact of relay 14 closes the operating circuit for motor magnet 34 and the arm 33 is thereby rotated until it engages the terminal individual to the line L Relays 21 and 31 thereupon operate over the circuit extending from battery, through the winding of relay 31, the arm 33 and the terminal engaged thereby, the winding of relay 21, the outer right-hand alternate contact of relay 14 and the normal contact of relay 22 to ground. The opening ot the left-hand normal contact of relay 31 disables the motor magnet 34 so that arm 33 remains in engagement with the terminal individualto the line L Relay 31 locks over the circuit extending from battery, through the winding and left-hand alternate contact of relay 31, andthe contact of relay 45 to ground. The closure of the right-hand alternate contact of relay 31 closes a circuit for the motor magnet 47 from battery, through the winding and contact of motor magnet 47, the left-hand normal contact of relay 41 and the right-hand alternate contact oi relay 31 to ground. In response to the operation of motor magnet 47, arms 42 and 43 rotate synchronously. The closure of the middle alternate contact of relay 21 connects ground to the terminal individual to the line L of the bank of terminals associated with arm 42. The closure of the left-hand alternate contact of relay 21 con-- nects the negative terminal of the battery to the interconnected terminals of the bank associated with the arm 43. When the arm 42 reaches the terminal individual to the line L relay 41 operates over a circuit extending from battery, through the winding of relay 41, the arm 42 and the terminal en gaged thereby, and the middle alternate contact of relay 21 to ground. The opening of the left-hand normal contact of relay 41 disables motor magnet 47 so that arm 42 is maintained in engagement with the terminal individual to the line L The closure of the alternate contact of relay 41 causes the op eration of relay 44 over a circuit extending from battery, through the winding of relay 44, the alternate contact of relay 41 and the normal contact of relay 45 to ground. Relay 44 thereupon locks over a circuit completed from battery, through the winding and left-hand contact of relay 44,v and the contact of relay 45 to ground. Upon each engagement of the arm 43 with a terminal or" the associated bank prior to the engagemeat 01 the arm 42 with the terminal individual to the line L circuit is completed from the negative terminal of battery,

through the left-hand alternate contact of relay 21, the terminal of the bank associated with the arm 43, the arm 43, the upper winding of relay 28, the common signaling conductor 80, through the windings of relay 29, and the artificial line AL to ground. In response thereto, relay 29 closes its upper contact causing the operation of relay 66 and motor magnet 68 over a circuit extending from battery, through the contact and winding of motor magnet 68, the right-hand winding of relay 66, and the upper contact of relay 29 to ground. In operating, upon response to the first of such impulses, relay 66 locks over a circuit extending from bat- Cit tery, through the left-hand winding and left-hand alternate contact to relay 66 and the. contact of relay 6a to ground. The motor magnet 68 causes the arms 61 and 62 to rotate synchronously until the terminal individual to the line L engaged by the arm 61 whereupon relay 71 is operated over a'circuit extending from battery, through the winding of relay 71, the terminal individual to the line L and the arm 61 to ground. Dce'to the operation of relay 71 and inasmuch as relay is at this time 0perated and locked to remove ground from its normal contact, relay 70 is released to disable the battery supply circuit for the filament forth'e repeater R restoring such repeater to normal. As in the previous case where the originating signal is transmitted from oiiice X to oiiice Z", the relays 63 and operate over the circuit extending from battery. through the windings of relays 61) and 63 in series, the left-hand alternate eontact of relay 71, and the contact of relay 6 1 toground. Relays 63 and lock over a circuit extending from battery, through the. winding of relay. and the winding oi: relay 63 in series, the right-hand alternate .contact of relay63 and the contact of relay 64 to ground. Motor magnet 68 thereupon commences to operate and cause the advancement of arms 61 and 62. The advancement of arm 61 opens the circuit for relay 71 which thereupon releases. When arm 61 reaches the last terminal of the associated bank, relay 64 is operated over a circuit ex tending from battery, through the ler"thand alternate contact of relay 63, the winding of relay 6 1, the terminal engaging arm 61 to ground. In operating, relay 64 causes the release of relays 63, 65 and 66 and opens the circuit of motor magnet 68 so that the arms 61 and 62 cease in their rotation. Although, each time the arm 62 engages a terminal of the associated bank prior to reaching the terminal corresponding to the line L an impulse of current of negative polarity is transmitted over the circuit ex tending from negative terminal of battery, through the right-hand alternate contact oi relay 66, the normal contact of relay 65, the terminal engaged by the arm 62, the arm 62, the upper winding of relay 128, the commen signaling conductor 180. both windings of relay 129 and the artificial line AL to ,J. ound, the polarity of such current produces no effect upon the circuit since relay 129 is adapted to close a contact in response to the oppositepolarity only. It more than one repeater station were used, however, these impulses wouid'cause relay 29 of the next repeater station to close its upper contact to open the filamentcircuit at its station.

When the operator at oiiice Z removes the plug 161 cf the lint: .ircuit B from the iat-l:

110. all apparatus of the system is returned to its normal condition and is prepared for the initiation of another call.

Although the operation of the system has been described in connection with a call originating at ofiice X and received at otiice Z, it is evident from the duplication of the apparatus at the oi'i'ices X, Y and Z that the calls may be originated at ofiice Z and trans mitted to oflice X through any desired number of repeater stations in a similar manner, the corresponding elements operating as described in connection with the signals which were described in the previous outline. It will be noted that the relays 70 and 170 con trol the repeater twpiipmcnt filament circuit and the need for the duplicate arrangement. one oi which responds to signals being received in one direction while the other responds to signals received from the opposite direction, is evident when it is considered that the signals may be sent in both directions at the same time for selecting or restoring the repeater equipment.

'What is claimed is:

1. In a telephone system the combination with a plurality of trunk lines and a signaling path common thereto extending between two stations, of a selective switch individual to said signaling path and means responsive to the taking for use of any one of the trunk lines and to the impression of current on said line for operating said selective switch to send over said common signaling path a series of impulses corresponding in number to the line taken for use.

2. In a telephone system the combination with a plurality of trunk lines and a signaling path common thereto extending between two stations, of a number of cord circuits for association with said trunk lines, a selective switch individual to said signaling path, means responsive to the association of one of said cord circuits with any one of said trunk lines and to the impression of a distinctive current on said trunk line for operating said selective switch to send over said common signaling path consecutive impulses of one polarity, and means responsive to the dissociation of said cord circuit from said line for operating said selective switch to send over said common signaling path a series of impulses of opposite polarity.

3. In a telephone system the combination with a plurality of trunk lines and a signaling path common thereto extending between terminal stations, of normally inoperative repeater equipment included in said trunk lines at intermediate stations, a number of cord circuits for association with said trunk lines at said terminal stations. a selective switch individual to said signaling path at each of said stations, means responsive to the associat on of one of said cord circuits with any one of said trunk lines and to the impression of a distinctive current on said trunk line for operating one of said selective switches to send over said common signaling path a series of impulses of which the number is controlled by the trunk line taken for use, means responsive to said impulses for operating the selective switch at said intermediate station, and means responsive to such operation of said switch to render operative the repeater equlpment included in the trunk line with which said cord circuit has been associated.

a. In a telephone system the combination with a plurality of trunk lines and a signaling path common thereto extending between terminal stations, of normally inoperative repeater equipment included in said trunk lines at intermediate stations, a number of cord circuits for association with said trunk lines at said terminal stations, a selective switch individual to said signaling path at each of said stations, means responsive to the association of any one of said cord circuits with any one of said trunk lines, and to the impression of a distinctive current on said trunk line for operating one of said selective switches to send over said common signaling path a series of impulses of one polarity, means operated in response to the dissociation of said associated cord circuit "from said trunk line for operating said selective switch to send over said signaling path a series of impulses of opposite polarity, means responsive to said first series of impulses for rendering operative the repeater equipment included in the trunk line with which said cord circuit has been associated, and means responsive to said second series of impulses for rendering said repeater equipment inoperative.

In a telephone system the combination with a plurality of trunk lines and a signaling path common thereto extending between terminal stations, of signals at said stations, a number of cord circuits for association with said trunk lines, selective switches having contacts individual to said trunk lines at each oi said stations, means responsive to the association of any one of said cord circuits with any one of said trunk lines and to the impression of a distinctive current on said trunk line for operating one of said selective switches to send over said common signaling path a series of impulses of which the number is controlled by the trunk line taken for use, means responsive to said impulses for operating another of said selective switches to select a contact individual to the calling line, and means responsive to such. selection for operating a signal individual to said line.

6. In a telephone system the combination with a plurality of trunk lines and a signaling path common thereto extending be tween terminal stations, a number of cord circuits for association with said trunk lines, signals individual to said t .nlr lines, si nals individualto said cord circuits, select switches having contacts individi' trunk lines at each of said static-i responsive to the association oi an said cord circuits with any one of id trunk lines and to the impression. of a distinctiv current on said trunk line for operating one of said selective switches to send over said common signaling path a series of impulses of which the number is controlled by trunk line taken for use, means responsive to said impulses for operat lg ano her oi said selective switches to select a contact individual to the callii'ig line, and means is sponsive to such selection for opcrati g a signal individual to said line, l sclecti" i switches being responsive to the in'iprec-isio-n of a distinctive current on one end oil said line after the association or a cord cncuit with the other end or said line to operate a signal individual to said cord circuit.

Q a V 7. In a telephone system the combination with a plurality of trunk lines and a signah ing path common thereto extend ng between terminal stations of normally inoperative re peater equipment included in said trunk lines at intermediate stations, signals asso ciated with each trunk line at said terr' i stations, means including a selective switch at each terminal station for controlling said signals, means including a selective switch at each intermediate station for controlling the repeater equipment thereat, and means responsive to the initiation of a call on any one of said trunk lines and to the impre sion of a distinctive current on said trunl. line for operating one of said selective switches at each station simultaneously.

8. In a telephone system tne combination with aplurality oi trunk lines and a signaling path con'mion thereto er siding between two stations, of a selective switch, and means operable when any one or said trunk lines is taken for use for opeintiu: said switch to send over said common na ling path a series oi? impulses corrcspomling in number to the line taken for use.

9. In a telephone system the combination with a plurality of trunk lines and a signaling path common thereto extending between two stations, of a number of cord circuits for association with said trunk lines, signals at one station each individual to one of said trunk lines, a selective switch individual to said signaling pat-h, means responsive to the association of one of said cord circuits with any one of said trunk lines at one station and the impression of a distinctive current on said trunk line for operating said switch to send over said; common signaling path a series of impulses of one polarity to operate the signal at the first named station individual to said trunk line, and means responsive to the disconnection of said cord circuit from said line for operating said switch to send over said common signaling path a series of impulses of opposite polarity.

10. A source of impulses, a repeater including a step-by-step switch for repeating impulses received thereby, signaling devices, means including a switch controlled by repeated impulses received there 3y for effecting the operation of a signaling device corresponding to the number of impulses received and after said impulses have ceased and means for maintaining this signaling device operated independently of said second mentioned switch.

11. In a signaling system, a plurality of transmission circuits interconnecting two stations, a normally inactive repeating arrangement included in each oi the transmission circuits, a. signaling path common to the transmission circuits and interconnecting the stations, means controlled by the selection of one of the transmission circuits at either station to transmit a signal over the signaling path, and means responsive to the transmission of the signal to render active the repeating arrangement included in the selected transmission circuit.

12. A signaling system comprising a. pair of stations, a plurality of transmission circuits interconnecting the stations, a repeater included in each transmission circuit, a common signaling path interconnecting the stations, andmeans at each station for controlling the repeater of any transmission circuit over the common signaling path.

13. In a telephone system, a telephone line, sources of impulses of diiferent charac teristics, and means including a repeater comprising a step by step switch for associating one of said sources of impulses with said line upon the seizure thereof and another of said sources therewith, upon its release.

1 1. In a telephone system, a plurality 01 lines, a cord circuit, a key associated therewith, an automatic switch common to said lines, means responsive to the actuation 01 said hey subsequent to the association of said cord with one of said lines for conditioning said switch to function with the seized line, a signal associated with said line, source of impulses, a repeater theretor comprising a step by step switch, a signal path, and means responsive to the association o't said automatic switch with said line for connecting the source of impulses to said repeater to transmit a set of impulses individual to said line over said signal path to eilect the actuation of said signal.

15. The method of signaling which cone prises translating alternating signaling current into a code of direct current in'ipulses, translating the direct current impulses into a step by step movement, translating the step by step movement into a code of direct current impulses, and translating the last said code of impulses into a steady signal indication.

16. In a signaling system, a combination vof means for producing dili'ercnt codes of current impulses, a repeater therefor comprising a step by step switch actuated in a particular manner for each code of impulses, signaling devices, and means including a switch controlled by each setting of the first mentioned switch in l'Qf70]lS6 to a particular code of impulses to cause the operation of the corresponding signaling device and means for continuing the operation of said signaling device independently of the means for operating it.

In witness whereof, I hereunto subscribe my name this 14th day of December A. 1)., 1921.

HARRY ii. MicDOL SALT, 

